1. Field of the Invention
This invention relates to urease inhibition especially as employed to converse soil applied urea. One more particular aspect of this invention relates to urease inhibited urea based fertilizer compositions which contain one or more organo boron acid derivatives as the urease inhibitors. Another particular aspect of this invention relates to methods of inhibiting the action of urease by use of such organo boron compounds, and methods of increasing plant yield through use of such methods of inhibition and the composition of this invention.
2. The Prior Art
It is well known in the art to use urea and urea compositions in fertilizers for application to the soil. The effective life of such fertilizers, however, is of short duration wherever microbiological activity exists in the soil to which the fertilizer is applied. This is due to the fact that urea is hydrolyzed rapidly, and nitrogen is lost in the form of ammonia, when urea is placed under or on the surface of moist soil which contains urease. Urease, a crystallizable enzyme occurring in numerous bacterial and fungi, as for example micrococcus urease, catalyzes the conversion of urea into ammonium carbonate which subsequently decomposes into ammonium bicarbonate and ammonia. The reactions are as follows: ##STR1## A portion of the ammonia thus formed is held by absorbing constituents of the soil and is available to plants as nutrient. However, up to 50% of the ammonia may be lost to the air. A further problem resulting from the action of urease is that the accumulation of ammonium in the soil and rise in soil pH can lead to several problems, including damage to germinating seedlings and young plants.
One approach to reduction of problems resulting from the activity of soil urease toward soil applied urea is to find compounds that inhibit urease activity when applied to soils in conjunction with fertilizer urea. This approach has received considerable attention, and several compounds have been used. For example, U.S. Pat. No. 3,388,989 discloses a fertilizer composition consisting of urea, a hydrocarbon binder and a urease inhibitor such as formaldehyde; boron metal salts, such as sodium borate and potassium borate; fluorine metal salts and heavy metal ions with atomic weights greater than 50.00. U.S. Pat. No. 3,523,018 describes the use of inorganic or organic heavy metal salts such as copper sulfate, borax, and addition compounds of cupric cyanide, boron trifluoride, copper formate and copper acetate as urease inhibitors. Lastly, U.S. Pat. No. 3,565,599 describes a fertilizer composition which contains urea, certain hydrophobic chemicals and an inorganic boron compound as for example orthoboric acid, sodium perborate, potassium metaborates, tetraboric acid, ammonium pentaborate and ammonium tetraborate.